Various methods are known in the literature for preparing Cu(I) carboxylates. In a simple but typical literature preparation, Cu(II) acetate is reduced to Cu(I) acetate in the presence of metallic copper. This reduction reaction is typically an extremely slow reaction with less than complete conversion of the Cu(II) acetate. There exists, therefore, the need for an economical preparation for Cu(I) carboxylates.
Cu(I) carboxylates have been found to be useful, among other things, as complexing reagents employed to separate unsaturated aliphatic hydrocarbons such as olefins from close boiling and difficulty separable saturated aliphatic hydrocarbons such as paraffins.
Various complexing reagents have been described in the prior art. However, difficulties exist with the previously known systems. For example, aqueous systems involving Cu(I) salts and ammonia or ammonium are corrosive and lack necessary long term stability. Non-aqueous Cu(I) solutions using a pyridine solvent have proven difficult to handle due to the solvent and require large scale systems because the reagent is in the form of a slurry in the solvent. Cu(I) sulfonic acid reagents have proven too viscous for easy handling; furthermore the strong heats of adsorption of these salts for olefins render the decomplexation difficult. Finally, Cu(I) salt and Lewis acid systems disclosed in the prior art have evidenced solubility problems and solvent alkylation problems.
There still exists the need for a complexing reagent which has a high olefin complexing capacity while providing for easy desorption of the olefin, has a high solubility in an inert solvent, has a favorable viscosity, is relatively stable, gives few side reactions during the complexing process, and can be prepared from cheap starting materials.